After establishing the mass production process of C60 in 1990, studies on fullerene have been extensively made, and various kinds of derivatives of fullerene have been synthesized and studied for possibilities of practical applicability thereof.
One of the fields among the practical applications of fullerene is a battery. Examples of the battery include a lithium secondary battery. A lithium secondary battery has a high energy density owing to the small atomic weight of lithium, and is used as an electric power source of such an electric equipment as a portable telephone and a personal digital assistant (PDA).
Examples of the technique using fullerene hydride obtained by adding hydrogen to fullerene as an additive for a carbon anode (International Application No. 00/31811). According to the investigations made by the inventors, however, it has been found that fullerene hydride is instable and has a tendency of being decomposed in a solvent, and thus cannot be added to a carbon anode stably, whereby the battery capacity is liable to become insufficient or instable.